Study Spots Early Warning Signal for Sudden Cardiac Death

Risk higher when electrical impulses travel more slowly through lower chambers of the heart

WEDNESDAY, May 23 (HealthDay News) -- The risk of sudden cardiac death is higher in men whose electrical impulses travel more slowly through the lower chambers of the heart, a new study indicates.

Electrical impulses travel through the heart and cause it to pump blood through its four chambers. The impulses, or waves, have distinct patterns and can be measured using an electrocardiogram (ECG). The waves traveling through the heart's lower chambers (ventricles) are shown on the ECG as the "QRS" complex.

In the new study, more than 2,000 Finnish men, aged 42 to 60, were followed for 19 years. During that time, 156 of the men died from sudden cardiac death, in which the heart suddenly and unexpectedly stops beating.

The risk of sudden cardiac death rose 27 percent for every 10 milliseconds increase in QRS duration. (A millisecond equals one-thousandth of a second.) Men with QRS durations longer than 110 milliseconds had a 2.5-fold higher sudden cardiac death risk than those with a QRS duration of less than 96 milliseconds, the investigators found.

QRS duration posed a higher risk of sudden cardiac death than other known risk factors, such as smoking, being unfit, overweight or having high blood pressure, the results showed.

Only a prior heart attack and having type 2 diabetes increased the risk of sudden cardiac death more than QRS duration, according to the study published online May 21 in the journal Circulation.

"Our study shows that QRS duration is one of the strongest risk factors for sudden cardiac death, although left ventricular function was taken into account," study author Dr. Sudhir Kurl, a researcher physician at the University of Eastern Finland, said in a journal news release. "We believe resting ECG should be used to help assess the risk of sudden cardiac death in particular patients."

Kurl and colleagues said that the people most likely to benefit from such testing include those with known cardiovascular disease risk factors and symptoms, and those who are inactive but plan to start an exercise regimen.

The researchers also said their findings apply to both men and women, other nationalities, and ethnic and racial groups worldwide.